Probability issues

I meet a problem when I am doing my homework, I don't know how to random which filed is affect. Please help! Thanks!



The amount of corn available, which we will call 푌 (measured in grams), is unknown, because it depends on how many of Cornucopia’s crop fields become infected with “stalk rot,” a disease affecting corn crops. Cornucopia grows corn in twelve fields, arranged consecutively along one bank of a river. Each field yields no corn if infected. If it is not infected, its yield is normally distributed with a mean of 160 kg and standard deviation of 20 kg.

Each field will be infected with stalk rot if and only if it contracts it in one, two or all three of the following ways:

 Any of the twelve fields can contract stalk rot from the wider environment, with a 20% chance.

 Any field other than the first (counting upstream to downstream) can contract stalk rot from its
upstream neighbour with a 70% chance, if that neighbour is infected.

 The 푛th field (if 푛 > 2) can contract stalk rot from the (푛 − 2)th field with a 15% chance, if
the (푛 − 2)th field is infected.

QUESTION

Create an Excel worksheet implementing 1000 simulations of
- the infection process, determining which of the 12 fields contracts stalk rot,
- the random corn crop yield from the uninfected fields,
- the total corn crop yield, and
- the resulting profit.

Determine the sample mean and sample standard deviation of simulated profits. Some suggestions:
- Firstly, just do one simulation.
- Use a row of 12 cells to represent (using the special values TRUE and FALSE) whether each field contracts stalk rot.

푛 is n, sorry.

Many thanks for you!